The subject matter of the present invention relates generally to heat insulated doorsill apparatus and in particular to such doorsill apparatus including an insulating spacer fastener which fastens inner and outer sill members of metal together against relative movement. A preferred embodiment of the invention includes an insulating spacer clip of synthetic plastic material which clips onto projections extending from the sill members to fasten such sill members together.
The present invention is especially useful in the construction of sliding glass patio doors and other exterior doors which include an outer sill member that is exposed to the exterior weather and atmospheric temperatures and an inner sill member that is at room temperature in the interior of the house or other building. The inner and outer sill members are thermally insulated from each other by the insulating spacer clip of the present invention, and are fastened together against relative movement by such clip for simplier and less expensive manufacturing of a door assembly employing such doorsill apparatus.
It has been proposed in U.S. Pat. No. 3,382,617 of St. Aubin granted May 14, 1968 to provide an insulated doorsill apparatus in which inner and outer sill members of metal are supported in insulating relationship by wood core members. A plastic bridging section which extends over the gap between the inner and outer sill members is employed to prevent moisture condensation and to provide an additional heat insulation. However, the plastic bridging section is not a clip member and does not fasten the inner and outer sill members together against relative movement. Instead, the bridge section is provided with an elongated slot which enables lateral movement of the outer sill member to accommodate doors of different size. The bridging section engages weather stripping on the bottom of the door to prevent cold air from passing from the exterior to the interior of the building.
U.S. Pat. No. 4,224,766 of Procton granted Sept. 30, 1980 shows an insulated threshold or doorsill apparatus having a plastic bridging member which is a thermal barrier and also forms a seal with the bottom of the door and is adjustable in height and width to accommodate different size doors. U.S. Pat. No. 3,061,896 of Wahlfeld granted Nov. 6, 1962 shows a similar teaching. A plastic joint member with keyed ends is provided in the Procton patent for holding inner and outer sill members together after they have been extruded as an integral member and then cut apart into two separate members. However, the plastic joint is not a clip member and does not clip onto projections extending from the inner and outer members. Instead, its keyed ends slide longitudinally within U-shaped channels provided in the inner and outer sill members which makes it difficult to install the joint member due to high friction. Also, the extruded channels increase the cost of the threshold. U.S. Pat. No. 3,346,994 of Kesler granted Oct. 17, 1967 shows a similar teaching for securing three metal members together. It is also known to provide similar thermal barrier members of plastic in window frames, such members being provided with keyed ends which are inserted longitudinally in keyway slots in the two metal members to be joined.
In the above patents, a wood core is employed to insulate and fasten the inner and outer sill members from each other which is not necessary in the insulated sill apparatus of the present invention. In addition, the plastic bridging section which also acts as a door seal is subject to wear due to abrasion by the bottom of the door, and the feet of people crossing the threshold. This is not a problem with the insulating spacer clip of the present invention because it is spaced below the upper surface of the sill members and is located at the bottom of the sliding door channel so that it is not subject to abrasive wear by either the door or by the feet of people crossing the doorsill.
The insulating spacer clip of the present invention enables the manufacture of insulated doorsill apparatus less expensively and more conveniently than that of the prior art. For example, it is presently the practice to form a thermal barrier, such as the plastic joint member 23 of the Procton patent by pouring liquid plastic, such as epoxy resin, into the channel space provided by the portions 21 and 22 of the sill member 12 which are extruded as an integral member before the slot 56 is milled out to separate such members. Of course, this is very time consuming and so expensive that a large number of doorsill apparatus must be manufactured at the same time to make it practical.